Fluid regulators are typically used to regulate the pressure of a fluid to a lower and/or substantially constant value. Specifically, a fluid regulator has an inlet that typically receives a supply fluid at a relatively high pressure and provides a relatively lower and/or substantially constant pressure at an outlet. For example, a gas regulator associated with a piece of equipment (e.g., a boiler) may receive a gas having a relatively high pressure from a gas distribution source and may regulate the gas to a lower, substantially constant pressure suitable for safe, efficient use by the equipment.
To prevent downstream pressure (i.e., outlet pressure) from reaching unsafe levels, fluid regulators often include over pressure protection devices (e.g., shut-off devices, true monitoring devices, etc). Over pressure protection devices are operatively coupled to the fluid regulator and activate (e.g., when the downstream pressure of the fluid reaches a predetermined value) to prevent unwanted (e.g., unsafe) build-up of pressure at the downstream source. Some over pressure protection devices (e.g., shut-off devices) shut-off the flow of process fluid to the downstream source until the over pressure protection device is manually reset.
However, in some instances, an increase in fluid pressure due to, for example, temperature variations, may cause an undesired or unwanted activation of the over pressure protection device. To prevent unwanted activation of the over pressure protection device, some known spring-loaded fluid regulators may have an internal relief valve. However, the internal relief valve may bleed excessive fluid (e.g., natural gas) to the atmosphere. Some applications and/or governmental regulations (e.g., European regulations) limit the amount of fugitive emissions that may vent to atmosphere. Thus, internal relief valves that vent fluid to the atmosphere in excess of the limits imposed by regulations may not be used in some applications.